It was thought strange when it was proved that Colias Keeivaydin and C. eurytheme were seasonal forms of a single species. Still stranger did it seem when Mr. W. H. Edwards proved by breeding that C. eriphyle (alias Hagenii) was also a form of eurytheme, but even after this I was not quite prepared for the conclusiton, forcced upon me by irresistible facts, that in this locality the orange and yellow forms were not only of one species, but actually alternated seasonally, the former being the summer, and the latter the winter form.